Conventionally, a self-power generating type bidet has been known, which generates power by using water introduced into a ceramic tank and supplies the generated power as a power to be used for the bidet.
However, the generator of the bidet is installed in a flow path of water introduced to the ceramic tank, and the power generated by the generator is used for the bidet. Therefore, the quantity of generated may be insufficient.
The generator used in the bidet is operated by the pressure of water supplied to a pipe of a toilet. FIG. 1 shows the construction of the generator using water pressure.
Referring to FIG. 1, the generator 10 includes a housing 11, an impeller 20, a shaft 30, a seal unit 17, a magnet (rotor) 40, and a bobbin (stator) 51. The housing 11 includes a water inlet 12 and a water outlet 13. The impeller 20 is rotatably fixed inside the housing 11. The shaft 30 is connected to the impeller 20. The seal unit 17 is closely attached to the shaft 30 to seal the shaft 30 such that water inside the housing 11 does not flow into the magnet 40. The magnet 40 is rotated integrally with the impeller 20 through the shaft 30. The bobbin 51 is disposed to surround the magnet 40.
In such a generator 10, the impeller 20 is rotated by the pressure of water introduced from a water supply source 15 through the water inlet 12. As the impeller 20 is rotated, the magnet 40 is rotated integrally with the impeller 20 to generate a current in the coil bobbin 51 serving as the stator.
At this time, the seal unit 17 of the generator 10 prevents the water rotating the impeller 20 from flowing into the magnet 40. However, the friction between the rotating shaft 30 and the seal unit 17 may interfere with the rotation of the shaft. Therefore, power generation efficiency may be decreased.
In order to solve such a problem, a generator has been developed (refer to FIG. 2). Although the magnet 40 comes in contact with water, it does not have an effect upon power generation. Therefore, the seal unit 17, positioned at the portion through which the shaft 30 passes in the housing 11, is removed from the generator, and a housing 16 for preventing water from flowing into the bobbin 51 is formed in the generator. However, when the housing 11 is constructed in such a manner, the housing is positioned between the magnet 40 and the bobbin 51, and internal pressure (water pressure) is applied to the housing. When the thickness of the housing is increased to endure the internal pressure of the housing, the distance between the bobbin 51 and the magnet 40 is increased. Then, the power generation efficiency may decrease. Therefore, the magnet 40 may be disposed in a housing formed of a metal. In this case, stability against internal pressure may be secured, and the distance between the bobbin 51 and the magnet 40 may be reduced.
As described above, when the housing is formed of a metal, stability against internal pressure may be secured owing to the small thickness thereof. However, the power generation efficiency may decrease due to an eddy current loss caused by the metal.